Efficient removal of tartrazine from aqueous solutions by solid sorbents

In this study we investigated the efficiency of a wide panel of 24 solid sorbents comprising layered structures (hydrotalcites and zirconium phosphates), magnesium oxide and hydroxide, phyllosilicates, silica, and alumina, as agents for the effective and high yield removal of tartrazine from its aqueous solutions. Quantification of this azo dyes was made by HPLC analyses of the filtrate after collection of sorbents. Overnight treatment of tartrazine solutions at a concentration of 10 mu g/mL with 100 mg of each solid sorbent resulted in a practically complete bleaching in 9 cases, namely Zn Al nitrate (99.9 %), Zn Al chloride (99.9 %), Mg Al nitrate (99.8 %), Mg Al azelate (99.9 %), Mg Al hydroxy chloride (99.9 %), zirconium phosphate (type B) + octadecylamine (99.9 %), MgO (99.8 %), and Mg(OH)2(99.7 %), out of 24. The most effective solids to this aim were seen to be aluminium based layered double hydroxides. The presence of this cation residues in the crystal structures of such sorbents seems to be a determinant in facilitating the adsorption of tartrazine by tight interaction with its sulfonate moieties. Recyclability and reuse of such solids have been assessed using Mg Al azelate as the reference. After its recovery and drying, five assays were accomplished under the same experimental conditions providing percentages of adsorption of tartrazine from its aqueous solution in the range 99.1 % - 99.6 %. The highest amount of tartrazine adsorbable on the most efficient sorbents have been obtained by adsorption isotherms and fall in the range 168.9-185.7 mg/g.

Automated summary

In this study, the efficiency of 24 solid sorbents for the removal of tartrazine from aqueous solutions was investigated, with aluminum-based layered double hydroxides being found to be the most effective sorbents.